Retaining screw with retentive feature

ABSTRACT

A dental retaining screw used to secure dental components, such as abutments, copings, and prosthesis to dental implants. The screw having a locking mechanism adapted to prevent the screw from loosening during shipping or while experiencing vibrations. The locking mechanism includes a locking component and biasing members located in the head portion of the retaining screw.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.10/302,253 filed Nov. 22, 2002, entitled “Retaining Screw With RetentiveFeature,” which claims the benefit under 35 U.S.C. 119(e) of U.S.Provisional Application Ser. No. 60/385,814, filed Jun. 4, 2002 andentitled “Retentive Screw With Retentive Feature,” both of theseapplications being hereby incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

FIELD OF THE INVENTION

The present invention relates generally to the field of dentalimplantology and, more specifically, to retaining screws used to securedental components, such as abutments, copings, and prosthesis to dentalimplants.

BACKGROUND OF THE INVENTION

Retaining screws in the field of dental implantology or dentalprosthetics are very important since they are used to fasten and holdtogether various dental components. These retaining screws, for example,fasten the dental abutment to the dental implant. Unfortunately, priordental retaining screws tend to loosen over time and also need internalthreads inside the abutment to prevent the screw from falling out. Theloosening of these screws has caused many problems, and much effort hasbeen devoted to solving these problems.

Dental retaining screws are typically fabricated from titanium. On onehand, titanium is ideal for this indication since it is strong,light-weight, and biocompatible. On the other hand though, titanium hasa high coefficient of friction that makes it very susceptible toloosening over time. Specifically, a large percentage of the torqueapplied to a dental retaining screw is lost to overcoming the highfrictional contact between the screw threads and threaded bore of theimplant and between the screw head and seating surface of the abutment.According to some estimates, approximately 50% of the applied torque islost in overcoming the mating friction under the screw head; and 40% ofthe applied torque is lost in the threads. As such, only about 10% ofthe applied torque exerted on the screw head is actually exerted aspreload or-tensile force stretching and tightening the screw.

Retaining screws tend to loosen in dental applications also becausethese screws are exposed to large loads and extended vibrations.Occlusal forces from chewing, talking, grinding, brushing, etc.continuously load the prosthetic tooth and accompanying retaining screw.These forces, over time, can decrease the preload and loosen the screw.Once the screw loosens, the joint between the prosthetic components canopen or form gaps. The dental components, such as the prosthesis, theabutment, and the screw, can then bend or even break.

Over the years, many solutions have been proposed to reduce theoccurrence of titanium screws loosening in dental applications. Onesolution is to increase the applied torque to the screw. This solutionhas limitations since the retaining screws can be tighten or loadedabove the yield point of the material. In this instance, the screw canbe permanently damaged and elastically unable to return to its originalshape and position. Further yet, the maximum, attainable preload can belessened if the screw is permanently damaged and deformed.

Many other solutions have been devoted to reducing the coefficient offriction either between the screw head and the mating surface of thedental component or between the screw threads and threaded bore of theimplant. In some instances, screws have been made of gold-alloy materialto reduce the co-efficient of friction, but their soft material causesdeformation of their threads upon tightening.

In other instances, surface coatings have been placed on the retainingscrew to reduce the coefficient of friction. U.S. Pat. No. 6,447,295,entitled “Diamond-Like Carbon Coated Dental Retaining Screws” andincorporated by reference herein, teaches a retaining screw coated withdiamond-like carbon. Further, U.S. Pat. No. 5,711,669, entitled “HighLoad Factor Titanium Dental Implant Screw” teaches a retaining screwcoated with a soft, deformable, biocompatible material that is malleableand subject to cold flow.

These coatings can reduce the coefficient of friction of the retainingscrew, but the coatings have disadvantages. First, the coatings can beexpensive. Additionally, they can wear over time or become removed orscraped during tightening. Further, although they can reduce thecoefficient of friction, they do not prevent or inhibit the retainingscrew from loosening or losing preload due to occlusal forces,vibrations during masticulation, and the like.

It would be advantageous to have a dental retaining screw that could beused to secure prosthetic components to a dental implant yet not beprone to loosen or fall out from the abutment.

BRIEF SUMMARY OF PREFERRED EMBODIMENTS OF THE INVENTION

The present invention is directed toward dental retaining screws used tosecure dental components, such as abutments, copings, analogs, cuffs,healing members, and prosthesis to dental implants. The retaining screwhas a proximal end with a locking mechanism. This mechanism includes amoveable locking component and a biasing member that are disposed in ahousing formed as a bore.

The dental component includes an internal cavity with a lockingmechanism along the interior surface of the cavity. The retaining screwfits inside this cavity and seats on a ledge to connect the dentalcomponent and implant. When the retaining screw is placed inside theabutment, the screw will not loosen and fall out. Specifically, thebiasing member biases the locking component partially out of the housingto engage and lock with the locking mechanism of the dental component.The locking mechanisms of the retaining screw and dental component,thus, engage to prevent the screw from rotating or losing preload whiletightened and connected to the implant.

One important advantage of the present invention is that once theretaining screw is tightened to a selected torque level, the lockingmechanisms prevent or reduce the possibility that the retaining screwwill loosen. The retaining screw will not tend to loosen even whenexposed to large loads and extended vibrations, such as occlusal forcesfrom chewing, clinching, grinding, talking, brushing, etc. Hence thestability of the dental implant system is improved and a secure andreliable fastening mechanism or coupling is provided between the dentalcomponent and the dental implant.

As a further advantage, the locking mechanisms of both the dentalcomponent and retaining screw are biocompatible and resistive tocorrosion. The retaining screw is also relatively inexpensive tomanufacture.

Accordingly, the present invention comprises a combination of featuresand advantages that overcome various problems, deficiencies, orshortcomings associated with prior devices. The various features andadvantages of the invention will be readily apparent to those skilled inthe art upon referring to the accompanying drawings and reading thefollowing detailed description of the preferred embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more detailed description of the preferred embodiment of thepresent invention, reference will now be made to the accompanyingdrawings, wherein:

FIG. 1 is a partial cross-sectional view of a dental implant systemsupporting a prosthetic tooth and having a retaining screw in accordancewith a preferred embodiment of the invention.

FIG. 2 is a side view of an assembled retaining screw according to theinvention.

FIG. 3 is a partial cross-sectional view of a retaining screw accordingto the invention.

FIG. 4 is a cross-sectional view of one embodiment of an abutmentaccording to the invention.

FIG. 5 is a partial cross-sectional view showing the abutment of FIG. 4with the retaining screw of FIG. 2.

FIG. 6 is a partial cross-sectional view of another embodiment of aretaining screw according to the invention.

FIG. 7 is a cross-sectional view of another embodiment of an abutmentaccording to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a dental prosthetic implant system 10 having featuresin accordance with one preferred embodiment of the present invention.The dental implant system 10 generally comprises a dental component 12(shown as an abutment), a retaining screw or bolt 14 (shown as anabutment retaining screw), and a dental implant, fixture, or root 16.The dental implant 16 is adapted to be received in a hole, osteotomy, oralveolar cavity in a jawbone of a patient. The retaining screw 14 servesthe purpose of fastening the abutment 12 to the implant 16.

The dental component 12 and retaining screw 14 can be commercialized asa dental kit. This dental kit may further include additional dentalcomponents known to those skilled in the art. Such dental componentsinclude dental copings, analogs, healing collars, healing abutments,cuffs, prosthesis, and the like.

In one preferred embodiment, the dental implant system 10 furthercomprises a dental restoration, prosthesis, or artificial tooth 18 Theabutment 12 supports the restoration 18 in the mouth of a patient. Therestoration 18 can be cemented to the abutment 12. Alternatively, or inaddition, a separate screw (not shown) can be used to mount and retainthe prosthesis 18 on the abutment 12.

As shown in FIGS. 1 and 4, the abutment 12 is generally elongated inshape and can have a variety of shaped exterior surfaces 21 adapted toseat and retain the prosthesis 18. For example, the abutment exteriorsurface 21 can be tapered, conical, cylindrical, straight, angled,contoured, or combinations thereof.

As the skilled artisan will recognize, the present invention can beembodied utilizing a wide variety of commercially available abutments.Thus, the abutment 12 can comprise, for example, the UCLA abutment orabutments sold by Centerpulse Dental Inc. of Carlsbad, Calif.

The abutment 12 has a top end 22, a bottom seating end/surface 24 forinterfacing or abutting with the implant 18, and an internal, throughcavity or bore 26. This cavity has a generally circular opening 28 atthe top end 22 and is adapted to receive the retaining screw 14. Thecavity 26 further includes an internal seating surface, shoulder, seat,or ledge 32 that serves as a seating surface for the head of the screw14. Preferably, the shoulder 32 is generally flat, annular or ring-likein shape, but other embodiments are known to those skilled in the art.

The shoulder or abutting surface 32 divides or partitions the throughcavity 26 into an upper generally cylindrical cavity, portion, orsurface 34 and a lower (or middle) generally cylindrical cavity,portion, or surface 36. The cavity 34 and cavity 36 are in communicationwith one another with the cavity 34 having a diameter larger than thatof the cavity 36.

The cavity 36 is further in communication with a generally hexagonalsocket, portion, or surface 38 at the bottom end 24 of the abutment 12.The hexagonal socket 38 permits anti-rotational mating, coupling, orattachment between the abutment 12 and implant 16.

As shown in FIG. 4, cavity 26 includes a locking mechanism 27 formedalong the interior surface of the bore. Preferably, the lockingmechanism is formed above a threaded section 29. This locking mechanismincludes a plurality of locking members 31. In this embodiment, theselocking members are formed as elongated channels or grooves that extendin a longitudinal or axial direction in the interior surface of thecavity 26. Preferably, the locking members are spaced about 6° to 18°apart.

Turning back to FIG. 1, the implant 16 can any be one of a wide varietyof dental implants, for example, a threaded implant, a cylindricalimplant, or a tapered implant, as are known in the art, such as atapered or straight Screw-Vent implant of Centerpulse Dental Inc. Theimplant 16 comprises a body or root portion 40 adapted to engage anosteotomy or alveolar cavity in the jawbone of a patient. The implantincludes a hexagonal post or protrusion 42 at a top end 44. A blindinternal threaded socket or bore 46 originates from the top end 44 andinto the implant body portion 40. The threaded socket 46 is adapted tothreadably engage the abutment retaining screw 14. A seating surface 48generally circumscribes the hexagonal post 42 to engage, contact, orabut against the opposing abutment seating surface 24. The implant bodyportion 40 may include a passage 50 formed to permit in-growth of boneand tissue for locking or anchoring the implant 16 in the osteotomy.

The hexagonal post 42 of the implant is configured to provideanti-rotational engagement with the abutment hexagonal socket 38 (FIG.4). Alternatively, a mating post may be provided at the bottom end ofthe abutment 12 to interlock with a corresponding mating socket at thetop end of the implant 16.

Turning now to FIGS. 1-3, the abutment retaining screw 14 is generallydimensioned and configured to adapt to a particular implant-abutmentpair. The retaining screw 14 generally comprises an upper head or capportion 60 in mechanical communication with a shank portion 62 thatextends downwardly therefrom. The shank 62 comprises a threaded portion64 having threads 66 adapted to threadably engage the threaded socket 46of the implant 16. The threaded portion 64 is in mechanicalcommunication with an upper non-threaded portion 68 and a lowernon-threaded portion 70 of the shank 62.

The screw head 60 is preferably generally cylindrical in shape andincludes a lower contacting, seating, or abutting surface 72 forengaging the opposed seating surface, or shoulder 32 of the abutment 14.Preferably, the contacting surface 72 is generally annular or ring-likein shape to generally conform to the shape of the abutment shoulder 32.Additionally, the screw head 60 preferably has a generally hexagonalcavity or socket 74 for receiving a torque wrench or other suitabletool.

Looking now to FIGS. 2 and 3, an important advantage of the presentinvention is illustrated. The retaining screw 14 includes a lockingmechanism 80 adapted to prevent the screw from loosening. The lockingmechanism includes a locking component 82 and a biasing member 84. Thelocking component and biasing member are located in a housing 86 that ispreferably formed in the screw head 60.

The housing 86 may have various configurations known to those skilled inthe art. As shown best in FIG. 3, it may be a lateral bore 90 thatextends completely through the screw head 60 and that is perpendicularto a longitudinal axis of internal cavity 26. Alternatively, the borecould merely extend partially into the screw head and not completelythrough it.

A stop member or plug 92 closes one end of the bore 90 and maintains thebiasing member 84 and locking component 82 in the housing 86. The otherend of the bore remains open. A ledge or lip 94 at the end of bore 90prevents the locking component 82 from exiting the housing while underbias from the biasing member.

As shown in FIG. 3, the biasing member 84 is a coiled spring, and thelocking component 82 is a ball or ball bearing. Preferably, the ball isformed of a hard material, such as ceramic, ruby, or silicone nitride.Preferably, the spring is formed of a biocompatible, corrosive resistantmaterial, such as titanium. Other materials include stainless steel(such as SS 17-4) coated with an amorphous diamond coating. Preferably,the spring is biocompatible and corrosive resistant.

Turning now to FIGS. 3 and 5, the coupling between the retaining screw14 and abutment 12 is shown in detail. The locking mechanism 86 of thescrew engages or locks with the locking mechanism 27 of the abutment.Specifically, when the abutting surface 72 of the screw seats with theabutting surface 32 of the abutment, the biasing member 84 biases thelocking component 82 against the internal surface of the cavity. Thelocking component slideably moves in bore 90 in a radial direction thatis perpendicular to a longitudinal axis of internal cavity 26. Thelocking component 82, thus, engages the locking members 31. Thisconnection or engagement prevents the screw from loosening or losingpreload while the screw is tightened or torqued with the implant.

The rotational force or torque required to disengage the lockingmechanism 86 of the screw from the locking mechanism 27 of the abutmentshould be greater than the forces tending to loosen the screw, such asvibrational and occlusal forces like chewing, grinding, talking,brushing, etc.

One skilled in the art will appreciate that the biasing member andlocking component can have various configurations and continue tofunction as a locking mechanism on the screw. The locking component, forexample, can be a pin, a button, a cylinder, other geometricconfigurations, or combinations thereof FIG. 6 shows one such alternateembodiment.

FIG. 6 shows a retaining screw 100 similar to the screw in FIGS. 2 and3. One difference is with the locking mechanism 102. Here, the lockingcomponent 104 includes two separate balls. Each ball is positioned atone end of bore 106 and is biased by one end of biasing member 108. Aledge, lip, or stop member 112 at each end of the bore prevents thelocking components from escaping the bore.

It will be appreciated that the present invention could incorporatemultiple locking components and biasing members in other configurationsas well. Multiple bores, for example, could be used to house multiplelocking components and biasing members.

Although FIG. 4 shows the locking members 31 as channels, one skilled inthe art will appreciate that the locking mechanism 27 can have variousconfigurations without departing from the scope of the invention. FIG.7, for example, shows an abutment 120 similar to the abutment 12 in FIG.4. This abutment 120, however, has a different locking mechanism 122.Here, the locking mechanism 122 includes a plurality of locking members124 formed as circular indentations or partial spherical indentations.These indentations could have various configurations, such as squares,spheres, rectangles, or other polygonal formations.

The present invention can be used with various dental implants anddental accessories, such as abutments, healing components, fixturemounts, copings, analogs, cuffs, or other dental components. Further, asunderstood by those skilled in the art, the precise configuration anddimensions of the various components of the retaining screw may varydepending upon the size of the implant or dental component. Theprinciples of the present invention can be applied to these variouscomponents. Further yet, while preferred embodiments of this inventionhave been shown and described, modifications thereof can be made by oneskilled in the art without departing from the spirit or teaching of thisinvention.

While preferred embodiments of this invention have been shown anddescribed, modifications thereof can be made by one skilled in the artwithout departing from the spirit or teaching of this invention. Theembodiments described herein are exemplary only and are not limiting.Many variations and modifications of the system and apparatus arepossible and are within the scope of the invention. Accordingly, thescope of protection is not limited to the embodiments described herein,but is only limited by the claims which follow, the scope of which shallinclude all equivalents of the subject matter of the claims.

1. A retaining screw for fastening a dental component to a dentalimplant, the retaining screw comprising: a head having a seating surfaceadapted to engage a seating surface inside a cavity of the dentalcomponent; a shank extending downwardly from the head and havingexternal threads adapted to threadably engage a threaded socket of thedental implant, wherein said seating surface inside said cavity of thedental component is disposed between said seating surface of said headand the implant; and a locking mechanism located at the head andincluding a locking component and a biasing member, the lockingmechanism adapted to prevent the retaining screw from loosening whilethe retaining screw is threadably engaged in the socket of the dentalimplant.
 2. The retaining screw of claim 1 wherein the locking componentis a ball, and the biasing member is a spring.
 3. The retaining screw ofclaim 2 wherein the ball and spring are housed in a lateral bore, andthe spring biases the ball against the cavity of the dental component.4. The retaining screw of claim 3 wherein the ball is formed of aceramic, and the spring is formed of a corrosive resistant metal.
 5. Theretaining screw of claim 4 wherein the ball is formed of one of ruby orsilicone nitride, and the spring is formed of one of titanium or steelwith a diamond coating.
 6. The retaining screw of claim 4 wherein thelocking mechanism holds the retaining screw with a preload force ofabout one ounce to about 1½ pounds.
 7. A retaining screw for fastening adental component to a dental implant, comprising: a body having aseating surface adapted to engage a seating surface of the dentalcomponent and an externally threaded shank adapted to threadably engagethe dental implant, wherein said seating surface of the dental componentis disposed between said seating surface of said body and the implant;and a locking mechanism located on the body and including a housing anda locking component and a biasing member located in the housing, whereinthe biasing member moveably biases the locking component, and thelocking mechanism is adapted to prevent the retaining screw fromloosening when threadably engaged with the dental implant.
 8. Theretaining screw of claim 7 wherein the housing is a lateral bore, andthe locking component slideably moves inside the bore.
 9. The retainingscrew of claim 8 wherein the locking component includes two balls. 10.The retaining screw of claim 9 wherein the biasing member is a springwith two ends, a first end biasing one of the balls, and a second endbiasing another of the balls.
 11. The retaining screw of claim 10wherein one ball partially projects out of one end of the lateral bore,and another ball partially projects out of another end of the lateralbore.
 12. The retaining screw of claim 7 wherein the biasing membermoveably biases the locking component to partially project out of thehousing.